Caption: Robert J. Oppenheimer (left) and Ernest O. Lawrence at Oppenheimer's New Mexico ranch in the 1930s. At the time, Oppenheimer (1904-1967) was professor of theoretical physics at the University of California at Berkeley and Lawrence (1901-1958) was professor of experimental physics there and director of the Radiation Laboratory. In 1939, Lawrence won the Nobel Prize for physics for his invention and development of the cyclotron; during World War II he adapted the cyclotron to separate the uranium isotope U235, needed for the atom bomb, from the common U238. In 1943, Oppenheimer became director of Los Alamos, the laboratory near his New Mexico ranch where the atom bomb was built.